Article summary and reader response FINAL - District heating and cooling systems

According to the website's post on "District heating and cooling systems", ENGIE(2013) plays a significant role in providing heating and cooling systems worldwide and describes how its systems utilize renewable energy to conserve the environment. The website post stated that the renowned urban climate control system company Tabreed had concluded ENGIE as the biggest supplier of urban cooling networks across the globe. The website post also stated that ENGIE has strived to increase the use of renewable energy to 50% in European urban networks since 2018. With renewable energy, ENGIE heating and cooling systems generate heat and chilled water and supply it to buildings through a dispensing and a returning pipeline. In addition, the website post mentioned that ENGIE's heating and cooling system had successfully reduced greenhouse gas emissions by utilizing biomass, geothermal, and marine thermal energy. Furthermore, ENGIE adopts a free cooling system to reduce CO2 emissions, electricity, water, and energy consumption in comparison to conventional air conditioning. 

While I agree the use of renewable energy in district cooling contributes to environmental conservation, seawater air conditioning system does create some adverse effects on the environment.

District cooling via seawater is a technology that is making significant strides in aiding energy conservation. Due to its nature of lower temperature, seawater is an ideal source for heat exchange in the cooling system. However, when seawater is adopted for district cooling, heated water from the building is exchanged with seawater via a heat exchanger and dispenses warm water back to the ocean. This contributes to a higher ocean temperature, which might not be adaptable for marine life. Hunt(2019) highlighted that the return of seawater to coastal ecosystems should be handled with care to minimize the impact on marine life. In addition, he stated that the ocean air outlet might receive a thermal shock and an increase in nutrients. Therefore, environmental contamination can be contributed by these factors, posing a threat to the ocean environment.

Furthermore, seawater district cooling creates an adverse impact on the environment by emitting toxic substances into the atmosphere. District cooling via seawater utilizes metal and alloy pipes for the exchange of water which are prone to corrosion. Due to the high concentration of electrolytes in saltwater, electrons from the seawater attracts metallic ions. As a result, the contact between metal ions and seawater leads to corrosion and emits toxic substances such as sulfur dioxide and carbon dioxide into the atmosphere. Hou, Gao, Cui, and Yin (2017) also highlighted that the corrosion of metals and alloys in seawater could lead to environmental pollution due to the potential leakage of toxic substances. Therefore, the use of seawater for district cooling should be considered in light of its negative impact on the environment.

Despite the negative impact created using seawater in district cooling, it is undeniable that the benefits of a district cooling system are much greater than its disadvantages. Singapore is an example of a country heavily reliant on conventional air conditioning due to its hot climate. This reliance on conventional cooling systems has contributed to global warming due to heat emissions. Therefore, district cooling is applied in Singapore to build an increasingly sustainable environment, as demonstrated in Marina Bay Sands. Based on the SP Group(n.d.) website, it was reported that their district cooling system in Marina Bay saves more than 40% in energy consumption across 20 buildings in the vicinity. McKenna(2020) also adds that Marina Bay’s utilization of centrifugal chillers with a large cooling capacity allows its chiller to produce six times the amount of energy than the norm, allowing for greater energy efficiency. In addition, Tey(2011) reports that chilled water production in Marina Bay reduced approximately 23,000 tonnes of CO2 emissions and 1.2 million cubic meters of water annually.

In conclusion, the use of renewable energy in district cooling systems does contribute to environmental conservation. However, negative impacts on the environment caused by the seawater district cooling may be overlooked when weighing the pros and cons.

Reference

ENGIE. (2013, February 21). District heating and cooling systems.  https://www.engie.com/en/businesses/district-heating-cooling-systems.

Hou, X. Y., Gao, L., Cui, Z. D., & Yin, J. H. (2017). Earth and Environmental Science 108 (2018). Corrosion and Protection of Metal in the Seawater Desalination, Tianjin, China. https://doi.org/10.1088/1755-1315/108/2/022037

Hunt, J. (2019, January 29). Keeping Chilled in a Warming World. CMarkits.  https://cmarkits.com/archives/2896

McKenna, J. (2020, July 28). Below the surface of Singapore lies the future of keeping cool. Spectra. https://spectra.mhi.com/below-the-surface-of-singapore-lies-the-future-of-keeping-cool#district-cooling-%E2%80%93-a-secret-weapon-in-the-battle-against-climate-change

SPgroup. (n.d.). Cooling & Heating 'Marina Bay District Cooling System'. https://www.spgroup.com.sg/sustainable-energy-solutions/our-low-carbon-solutions/cooling-and-heating

Tey, PK. (2011). District Cooling System at Marina Bay, Singapore[Unpublished manuscript]. Singapore District Cooling Pte Ltd. https://www.districtenergyaward.org/wp-content/uploads/2012/10/District_cooling_Singapore_2011.pdf